Oxidation of hydrocarbons with sulfur dioxides



OXIDATION OF HYDRGCARBONS WITH SULFUR DIOXIDES Thomas H. Strickland andAlan Bell, Kingsport, Tenn., assignors to Eastman Kodak Company,Rochester, N.Y., a corporation of New Jersey No Drawing. ApplicationNovember 22, 1957 Serial No. 698,043

4 Claims. (Cl. 260-599) This invention relates to a novel process forthe oxi dation of alkylated benzene hydrocarbons. cific aspect thisinvention relates to a process for the oxidation of monoalkylated anddialkylated benzene hydrocarbons in the vapor phase with sulfur dioxideto form aromatic aldehydes. In a more specific aspect, this inventionrelates to the oxidation of toluene with sulfur dioxide in the vaporphase to form benzaldehyde.

This application is a continuation-in-part of ourv copending applicationSerial No. 590,809, filed June 12, 1956, now Patent No. 2,821,552.

In the prior art, alkylated aromatic hydrocarbons have been oxidizedwith a variety of oxidizing media, for example, steam, oxygen, which maybe in the form of air, and the like. In some instances, sulfur dioxidehas been employed along with the oxygen or other oxidizing medium inorder to control the reaction. However, the prior art procedures havenot recognized the fact that sulfur dioxide itself can be used as theoxidizing medium for alkylated aromatic hydrocarbons.

in accordance with this invention, it has been found that sulfur dioxidecan be used as the sole source of oxygen for the oxidation of alkylatedbenzene hydrocarbons to form a product containing a substantial amountof an aromatic aldehyde and substantially no aromatic acids.

The alkylated benzene hydrocarbons that are oxidized in accordance withthis invention are benzene derivatives containing one or two methylgroups or substituents, i.e. toluene and the xylenes. When the benzenenucleus contains a single methyl radical the resulting oxidation productis either predominantly or solely benzaldehyde.

, When the benzene nucleus contains more than a single methylsubstituent, such as a xylene, the resulting product is usually amixture of aromatic aldehydes.

-In practicing this invention, sulfur dioxide is the sole source ofoxygen for the oxidation reaction. If desired, inert gases, such asnitrogen, carbon dioxide and the like, can be employed to control thereaction; however, these inert gases are not essential to the carryingout of the reaction.

The process of this invention is usually carried out by passing amixture of sulfur dioxide vapor and hydrocarbon vapor at atmosphericpressure over a heated catalyst for the reaction. Among the catalyststhat can be used for the reaction are oxides of heavy metals in groupVA, VIA and VIII of the periodic table. For example, oxides of metals,such as vanadium, molybdenum, tungsten, chromium, iron and nickel can beused as catalysts for the reaction. The oxides of vanadium and tungstenare the preferable catalysts for this reaction. If desired, thesecatalysts can be supported on a suitable supporting material such asalumina, silica and the like.

\As indicated above, the reaction is ordinarily carried out atatmospheric pressure and an elevated temperature. In order to produce aproduct free of aromatic acids a temperature substantially below 350 C.is employed, and usually the temperature is within the range In a spenite Sttes Pateti'tO 2,928,879 Patented Mar. 15, 1960 pressures can beused, but atmospheric pressure is preferred for the process.

The oxidation reaction takes place between the sulfur dioxide andhydrocarbon to form the aldehyde in the absence of any other oxidizingmeans in the following manner;

It is, of course, to be realized that in this equation, toluene ismerely representative of the hydrocarbons that can be oxidized inaccordance with this process. It is evident from this equation that thehydrocarbon and sulfur dioxide can be employed in the reaction inequimolar ratios. If desired, an excess of hydrocarbon can be employedtocarry out the reaction. When an excess of hydrocarbon'is used, theexcess gas forms a diluent for the reaction in' the same manner in whichnitrogen or other inert gas can be used to control the reaction.

[In oxidation procedures, wherein a hydrocarbon is oxidized in the vaporphase with air or oxygen, the resulting oxidation products are mixedoxygen-containing compounds. However, when the same hydrocarbon isoxidized in the vapor phase with gaseous sulfur dioxide, under theconditions herein set forth, the resulting oxidation product is usuallyonly one oxygen-containing compound. For example, if toluene is oxidizedwith air over vanadium oxide as a catalyst, the product of the reactionis a mixture of benzaldehyde, benzoic acid and maleic acid. However,when toluene is oxidized with gaseous sulfur dioxide under theconditions herein set forth, using a vanadium oxide catalyst, theproduct is primarily benzaldehyde. In the process of this reaction, thepresence of benzoic acid has not been detected in the reaction product.

The following examples are illustrative of this invention:

Example 1 A gaseous mixture containing 74.4% toluene, 22.8% sulfurdioxide and 2.8% nitrogen at atmospheric pressure was passed intocontact with a catalyst mass of vanadium oxide on alumina at 310 C. Thesuperficial velocity was 54.5 feet per hour, and the apparent contacttime was 6.9 seconds. The reaction proceeded smoothly with theproduction of benzaldehyde, sulfur, unreacted toluene and water.Unreacted toluene was separated from the reaction product andrecirculated through the apparatus with additional sulfur dioxide. Theyield of benzaldehyde based on the toluene consumed was Benzoic acid wasnot detected in the reaction products.

Example 2 A catalyst mass of vanadium oxide on alumina was maintained at315 C. and contacted with a gaseous mixture containing 73.5% toluene,23.8% sulfur dioxide and 2.7% nitrogen at atmospheric pressure. Thesuperficial velocity was 50 feet per hour and the apparent contact timewas 6.5 seconds. The reaction proceeded smoothly with the production ofbenzaldehyde, sulfur, unreacted toluene and water, and unreacted toluenewas recycled. The yield of benzaldehyde based on the sulfur dioxideconsumed was Benzoic acid was not detected in the reaction products. i

In order to demonstrate the results obtained when higher reactiontemperatures are employed, the following example is included. 7

Example 3 A gaseous mixture of toluene, sulfur dioxide and nitro; genwas contacted at atmospheric pressure with a catalyst mass of vanadiumoxide on alumina at 370 C. The superficial velocity was 432 feet perhour and the apparent contact time was 0.75 second. The reactionproceeded smoothly with the production of benzaldehyde, benzoic acid,sulfur and water, and unreacted toluene was recirculated with additionalsulfur dioxide. The yield of benzaldehyde based on toluene consumed was3.95%.

In the above examples, space velocity designates the volume of gas (atreaction temperature and at atmospheric pressure) circulated per hourper unit volume of catalyst. The apparent contact time is the reciprocalof the hourly space velocity converted to a base of seconds, and thesuperficial velocity designates the volume of gas (at reactiontemperature and at atmospheric pressure) circulated per hour per unit ofcross sectional area of the catalyst bed.

Example4 In accordance with the procedure described in Example 1,o-xylene, m-xylene and p-xylene are oxidized with sulfur dioxide to formthe corresponding monoand dialdehydes.

In our copending application aromatic hydrocarbons were oxidized withsulfur dioxide at elevated temperatures of 350 C. and higher, and atthese conditions the oxidation reaction product was found to contain asubstantial amount of aromatic acids. Under the conditions em ployed inthe present process it is possible to produce an oxidation reactionproduct containing substantially no aromatic acids.

We claim:

1. The process for oxidizing a hydrocarbon selected from the groupconsisting of toluene and the xylenes which comprises contacting saidhydrocarbon and sulfur dioxide, as the sole source of oxygen for thereaction, said reactants being in the gaseous phase, with a heavy metaloxide catalyst selected from the group consisting of the oxides of heavymetals in groups VA, VIA and VIII of the periodic table at a temperatureof 275-330 C. and at a contact time of 3 to 7 seconds to form a productcontaining an aromatic aldehyde and substantially free of aromaticacids.

2. The process for oxidizing a xylene which comprises contacting saidxylene and sulfur dioxide, as the sole source of oxygen for thereaction, said reactants being in the gaseous phase, with a heavy metaloxide catalyst selected from the group consisting of the oxides of heavymetals in groups V|A, VIA and VII-I of the periodic table at atemperature of 275-330 C. and at a contact time of 3 to 7 seconds toform a product containing benzaldehyde and substantially free of benzoicacid.

3. The process for oxidizing toluene which comprises contacting saidtoluene and sulfur dioxide, as the sole source of oxygen for thereaction, said reactants being in the gaseous phase, with a heavy metaloxide catalyst selected from the group consisting of the oxides of heavymetals in groups VA, VIA and VIII of the periodic table at a temperatureof 275-330? C. and a contact time of 3-7 seconds to form a productcontaining benzaldehyde and substantially free of benzoic acid.

4. The process for oxidizing toluene which comprises contacting acidtoluene and sulfur dioxide, as the sole source of oxygen for thereaction, said reactants being in the gaseous phase, with a vanadiumoxide catalyst at a temperature of 275-330 C. and a contact time of 3-7seconds to form a product containing benzaldehyde and substantially freeof benzoic acid.

References Cited in the file of this patent- UNITED STATES PATENTS1,636,854 Craver s July '26, 1927 1,636,855 Graver -.s n n July 26, 19272,199,585 Bone et al. May 7, 1940 2,821,552 Strickland et al. Jan. 28,1958 FOREIGN PATENTS 408,184 Germany Sept. 28, 1920 OTHER REFERENCESKarrer: Organic Chemistry, 4th ed. (1950), p. 504.

1. THE PROCESS FOR OXIDIZING A HYDROCARBON SELECTED FROM THE GROUPCONSISTING OF TOLUENE AND THE XYLENES WHICH COMPRISES CONTACTING SAIDHYDROCARBON AND SULFUR DIOXIDE, AS THE SOLE SOURCE OF OXYGEN FOR THEREACTION, SAID REACTANTS BEING IN THE GASEOUS PHASE, WITH A HEAVY METALOXIDE CATALYST SELECTED FROM THE GROUP CONSISTING OF THE OXIDES OF HEAVYMETALS IN GROUPS VA, VIA AND VIII OF THE PERIODIC TABLE AT A TEMPERATUREOF 275-330*C. AND AT A CONTACT TIME OF 3 TO 7 SECONDS TO FORM A PRODUCTCONTAINING AN AROMATIC ALDEHYDE AND SUBSTANTIALLY FREE OF AROMATICACIDS.